Automatic polishing machine



Nov. 17, 1970 w. E. REASER EI'AL AUTOMATIC POLISHING MACHINE 7 Sheets-Sheet 1 Filed June 49 1968 JNVENTORS WARREN B. HEAsER, .EAHLE M. Paw 5, J12.

FIE-l- ATTYQ.

' 7 Sheets-Sheet 2 I I IiRHEN E. EBA 25. 2, .EA LEA/[.1 0 H5, JR.

Nov. 17, 1970 w. E. REASER EI'AL I AUTOMATIC POLISHING MACHINE Filed June 19, 1968 v I 062: "a \gg II 5-5-1? $2 w. E. REASER ET AL 3,540,158

Nov. 17, 1970 AUTOMATIC POLISHING MACHINE Filed June 19, 1968 7 Sheets-Sheet 5 INVENTORS.

I IZARREN E. HEAEER 41213 M. 1 012125125. J12.

v I Z6 TIE-4- Z 9%.

By ATTY Nov. 17, 1970 w. E. REASER ETAL 1 8 I AUTOMATIC POLISHING MACHINE Filed June 19. 1968 7 Sheets-Sheet 4.

INVENTORS: I WARREN EHEAEER,

I IE! 5 5 EARLE MP WERS, JR.

I .BY

AT YB.

Nov. 17,1970 w. E. REASER ETAL 3,540,158

AUTOMATIC POLISHING MACHINE 7 Sheets-Sheet 5 Filed June 19.- 1968 V/ q 0/ 6 9 0 mm 2| fimw o S X L 7/ 8E a, mm m s GU M fw ww 5 .I F? d/Z UF 5 u Z.i.@ B 5 4 HA 0 FR 2 I .JJFNTORS WARREN E. Hm 5512, .EAHLE M. Pun EH5, JR.

. Nov.17, 1 970 w. E. REASER ETAL 3,540,158

, AUTOMATIC POLISHING MACHINE Filed June 19. 1968 7 S hgets-Sheet s 5' /40 /36 /45 INVENTORS: A36 WARREN E. PEA SEE,

/37 I [j -g .E'AHLE M. POWERS, JR.

Nov. 17,1970 w. E. REASER ETAL 3,540,158

AUTOMATIC POLISHING MACHINE Filed June 19.' 1968 7.Sheets-Sheet 7 /4l' /4& 47 2 7 /47 6 ga A56 4 2 M7 //7 //6 INVENTORS: v WARREN 5122115212,

3,540,158 AUTOMATIC POLISHING MACHINE Warren E. Reaser, Brooklyn, Mich., and Earle M. Powers, Jr., Toledo, Ohio, assignors to Sun Tool & Machine Company, Toledo, Ohio, a corporation of Delaware Filed June 19, 1968, Ser. No. 738,267 Int. Cl. B24b /00 U.S. Cl. 51-133 8 Claims ABSTRACT OF THE DISCLOSURE A machine for lapping and polishing the surfaces of small workpieces such as automobile rearview mirrors and the like. The machine includes a frame, a horizontal polishing table rotatably mounted on the frame on a vertical axis, an independently rotatable head mounted above the table coaxially with the table, and a plurality of individually rotatable fixtures that are carried by the head and rotatable on axes parallel to the axis of the head. The fixtures have means for holding a plurality of workpieces in contact with the surface of the rotatable table onto which a grinding compound is supplied. Each of the fixtures is movable axially relative to the head in order to lift the workpieces out of contact with the surface of the rotatable table when the fixture rotates to a predetermined loading position to allow finished workpieces to be removed from the fixture and raw workpieces to be inserted. The machine has drive mechanisms for rotating the table, the head and the fixtures, and control mechanism which stops the rotation of each fixture and causes it to be elevated at the loading position.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a machine used for lapping and/or polishing the surfaces of glass pieces, and the like, and has particular utility when used to lap or polish rearview mirrors of automobiles.

Rearview mirrors of automobiles are conventionally made by cutting blanks from sheets of glass, rough grinding the blanks to the desired degree, and then lapping and polishing them to remove surface irregularities. Lapping is an intermediate step between rough grinding and polishing. Substantially, the only difference between lapping and polishing is in the nature of the abrasive used. The abrasive used in the lapping operation is generally aluminum oxide or garnet, whereas rouge is conventionally used in the polishing operation.

Automobile rearview mirrors which are adjustable for day or night driving have an angled surface relative to the back side thereof. It is extremely important that the mirror be ground to the proper angle and the surface be completely smooth in order to eliminate distortion.

The prior art In the prior art, automobile rearview mirrors were first rough ground on one machine, and then transferred to a second machine for fine grinding or lapping, and to still another for polishing. A typical machine used for this purpose consists essentially of a large rotating table (about 42" in diameter), and an opposing rotating fixture of approximately the same diameter. A plurality of mirror blanks (usually 40 or more) are adhered to the fixture with hot pitch. After each operation, in order to maintain the blanks in the same attitude for the subsequent operation, the entire fixture is removed from the first machine and transferred to a second or third machine. Because of the heavy weight of the fixture, two or more men are required to effect the transfer. In addition, there is con- United States Patent O ice siderable down time in transferring from one machine to another. This is, of course, uneconomical and undesirable.

SUMMA-RY OF THE INVENTION In general, the machine comprises a frame having a horizontal polishing table rotatably mounted on a vertical axis. Mounted above the table on the same axis is an independently rotatable head. A plurality of individually rotatable fixtures are carried by the head and are individually rotatable on axes parallel to the axis of rotation of the head. The fixtures hold the workpieces in contact with the table when in normal operative position. The workpieces are held in place on the fixtures by a vacuum system and are urged against the table by air pressure. Each fixture is movable between a lower working position adjacent the table and an upper loading position by an air cylinder. Driving means are mounted on the frame to rotate the table, the head, and the fixtures.

Switching means are mounted on the apparatus to actuate the air cylinder associated with each individual fixture when the fixture reaches a loading station at a predetermined position of rotation. The cylinder raises the fixture allowing the finished workpieces to be removed, and new ones inserted. When the fixture reaches another predetermined position, air to the cylinder is reversed and the fixture resumes its original position.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view in elevation of a machine embodying the invention with parts broken away, some parts in section and parts shown in phantom;

FIG. 2 is a plan view taken from the position indicated by the line 22 of FIG. 1 and showing the driving means for the head of the machine and a portion of the driving means for the fixtures;

FIG. 3 is a horizontal sectional view taken along the line 3-3 of FIG. 1 and showing another portion of the driving means for the fixtures;

FIG. 4 is a vertical sectional view on an enlarged scale, of the machine taken generally along the line 4-4 of FIG. 1, with parts broken away;

FIG. 5 is a fragmentary, horizontal sectional view taken along the line 5-5 of FIG. 1, with parts broken away and parts in phantom, and showing various air and vacuum connections and valve means of the machine of this invention;

FIG. 6 is a diagrammatic illustration of the air and vacuum system of the machine of the invention;

FIG. 7 is a fragmentary, diagrammatic view illustrating the sequential actuation of certain valving;

FIG. 8 is a fragmentary, plan view of an individual fixture of the machine of the invention, shown on an enlarged scale relative to FIG. 1;

FIG. 9 is a fragmentary, vertical sectional view with parts broken away, taken along the line 99 of FIG. 8;

FIG. 10 is a fragmentary, vertical sectional view taken along the line 1010 of FIG. 8; and

FIG. 11 is a fragmentary view in perspective of a of a fixture.

DESCRIPTION OF PREFERRED EMBODIMENT In the preferred embodiment of this invention, a main frame 10 has an upper half 11 and a lower half 12. The lower half 12 comprises a horizontal base plate 13 and heavy, vertical plates forming sides 14, a back 15, and an arcuate front 16 welded together to form a rigid enclosing hollow structure. The hollow structure thus formed is braced by a cross bridge 17. A horizontal flange 18 extends around the top edges of the sides 14, and back 15, for supporting the upper half 11.

The machine can be leveled by means of leveling screws 19 which are threaded through the base plate 13 at four approximate corners.

A table drive motor 20 (see also FIG. 3) is mounted on a gib 21 in a way 22 that is secured to one of the sides 14. The motor 20 is movable horizontally by an adjusting bolt 23 threaded through the back 15 into an ear 24 of the gib 21. A sprocket 25 on a shaft 26 of the motor 20 is engaged by a drive chain 27 which also engages a driven sprocket 28 mounted on and keyed to a vertically extending table drive shaft 29. The lower end of the drive shaft 29 is journaled by a bearing 30 attached to the base plate 13 in the center thereof by screws 31 which extend through a flange 32 in a bearing housing 33 and into the base plate 13.

A horizontal support plate 34 (see FIG. 4) is welded to the sides 14, back 15 and front 16, and rests on cross members 35 of the bridge 17. The upper end of the table drive shaft 29 extends through a central opening 36 in the support plate 34, and a bearing 37 mounted on the plate 34. The bearing 37 is protected by a shroud 38 that also is mounted on the plate 34.

A conduit 39 (FIG. 1) leads from an orifice 40 in the support plate 34 through the side 14 for disposal of grinding or polishing material which flows into the well formed by the support plate 34 and the upper parts of the sides 14, back 15, and front 16 of the lower half 12 of the frame 10.

A head 41 of the table drive shaft 29 protrudes through a top opening 42 in the shroud 38. A hub 43, removably connected by machine screws 44 to the head 41, supports a heavy circular table 45, preferably fabricated from cast iron. The heads of the screws 44 are accessible through a central opening 46 in the table 45.

The upper half 11 of the frame 10 comprises a horizontal plate 47 (see FIG. 3) which rests on the flange 18 of the lower half 12, covering the rear corners of the lower half 12, and which supports a vertically extending semi-cylindrical side plate 48 that is welded thereto. A top plate 49 (FIGS. 1 and 4) is welded on the top edge of the side plate 48. The top plate 49 is supported also by internal triangular braces 50. A protective cover 51 for the machine is mounted on the top plate 49 by screws 51a and has a front, lower portion 52 enclosing portions of the mechanism to be described below. The upper half 11 of the frame 10 is connected to the lower half 12 by heavy bolts 53 which extend through the edges of the plate 47 and the flange 18. The bolts 53 are secured by nuts 54.

A head drive motor 55 (FIG. 4) is mounted on the top plate 49 by screws 56 on a gib plate 57 which slides in a way plate 58. The motor 55 is movable horizontally by an adjusting bolt 59 which extends through an ear 60 on the top plate 49 and is threaded into an ear 61 of the gib plate 57.

The motor 55 drives a reduction gear box 62 by means of a belt 63 engaging a pulley 64 on a shaft 65 of the motor 55 and a pulley 6-6 on an input shaft 67 of the gear box '62. A drive sprocket 68 is mounted on a vertically extending output shaft 69 of the gear box 62.

A vertically extending, hollow cylindrical housing 70 (see FIGS. 4 and 6), is mounted at the front center of the top plate 49 and extends above and below the top plate 49 being secured thereto by machine bolts 71 which extend through a heavy annular flange 72 which lies on the top plate 49. Bearings 73, mounted in the upper and lower ends of the housing 70, journal a tubular head drive shaft 74.

As can best be seen in FIG. 6, a two-line rotary coupling 75 is mounted on the upper end of the shaft 74. An air conduit 76 and a vacuum conduit 77 are connected to ports in a sleeve 78 which is retained against rotation. A rotating body 79 has an inner air passageway 80 opening radially into an annular groove 81 and an inner vacuum passageway 82 opening radially into a similar til annular groove 83. Snap rings 84 retain the body 79 in place in the sleeve 78 with the ports of the air conduit 76 and vacuum conduit 77 aligned with the annular grooves 81 and 83, respectively. 0 rings 85 seal the body 79 in the sleeve 78. The rotary coupling 75 is attached to the top of drive shaft 74 by means of a collar 86. The air passageway 80 and vacuum passageway 82 in the body 79 have nipples 87 for connection to an air line 88 and a vacuum line 89 extending downwardly through the tubular shaft 74.

A sprocket 90 (FIG. 4) is keyed to the shaft 74 below the coupling 75 and above the housing 70. The sprocket 90 is connected by a drive chain 91 (FIG. 2) to the sprocket 68 of the reduction gear box 62. A movable idler sprocket 92 (see also FIG. 2) is mounted on the drive shaft housing 70 and engaged with the chain 91 in order to adjust tension in the chain 91.

A six-sided head 93 (FIGS. 3 and 4) comprises upper and lower plates 94 and 95 which are welded to the end of the shaft 74 beneath the housing 70. Three spider spindle brackets 96 are secured to alternate facets of the head 93, extending outwardly and downwardly therefrom and spaced 120 from each other. Each of the brackets 96 comprises two spaced, parallel, vertical plates 97, a horizontal brace plate 98 and a vertical end plate 99. The plates 99 have rectangular cut outs 100.

A tubular spider spindle 101 (see also FIGS. 8 and 9) is journaled by bearings 102 mounted one at the top and one at the bottom of the plate 99, a vacuum conduit 103 extends downwardly through the spider splindle 101 and the annular space between the vacuum conduit 103 and the wall of the spindle 101 forms an air conduit 104 which extends through its length. A rotary coupling 105 is mounted on the upper end of each of the spindles 101. A spindle drive pulley 106 is pinned on the spindle 101 just below the rotary coupling 105.

An air cylinder 107 that is supplied by lines 108 and 109 (FIGS. 5 and 6) is mounted on the horizontal plate 98 in the bracket 96 and its piston rod 110 extends through an opening 111 in the brace plate 98. An arm 112 extends radially through the cut out 100, and is connected by thrust collars 113 and a thrust bearing 114 to the spider spindle 101. As will later be described in detail, when air is admitted through the line 108 to the top of the cylinder 107, its piston rod 110 is extended downwardly to lower the spindle 101 and a fixture 115 carried thereby into polishing position.

One of the fixtures 115 (see FIGS. 8-11) is mounted on the lower end of each of the spider spindles 101. Each of the fixtures 115 comprises a horizontal disk shaped loading guide 116 having a plurality of cut outs 117 in the approximate shape of the workpiece to be treated. In the embodiment shown, there are three cut outs 117. The loading guide 116 is attached to a spindle drum 118 by screws 119 and the spindle drum 118 is in turn attached to a hub 120 mounted on the end of the spider spindle 101. A support bracket 121 for each of the cut outs 117 is attached to the drum 118 by screws 122 extending through a spacer 123.

An air cylinder 124 is mounted on each support bracket 121 directly over the corresponding cut out 117 in the loading guide 116, and its piston rod 125 extends downwardly through an opening 126 in the support bracket 121. An air line 127 is coupled to the air cylinder 124 at a level beneath its piston 128 and to an air passage 129 in the hub 120 which communicates with the air conduit 104 in the spindle 101.

The end of the piston rod 125 extends through a counterbored opening 130 in a retainer 131 and a cap 132 is threaded onto its lowermost end. The cap 132 is thus positioned in an enlarged pocket 133 formed in the undersurface of the retainer 131. The retainer 131 is secured to a pressure plate 134 by machine screws 135 (FIG. 10). The pressure plate 134 has a bevelled bottom surface 136 that is complementary to an angle to be ground on the surfaces of workpieces 137 to be polished. A vent 138 extends upwardly from the surface 136 to the pocket 133. A pair of generally rectangular pockets 139 (FIG. are cut in the undersurface of the pressure plate 134 and each of them is surrounded by a cushion 140.

The pockets 139 are connected by vacuum lines 141 to a manually operated valve 142. A vacuum line 143 connects the valve 142 to a radial passageway 144 (FIG. 9) in the spindle drum 118 and to a central vacuum chamber 145 communicating with the lower end of the vacuum conduit 103. A manual valve handle 146 is provided for actuating the valve 142. When the valve 142 is opened to connect the pockets 139 through the vacuum lines 141 to the vacuum conduit 103, negative pressure in the pockets 139 functions to retain a workpiece 137 against the cushions 140 on the bottom of the pressure plate 134. Conversely, when it is desired to remove a polished workpiece 137, the valve 142 is closed, releasing the negative pressure in the pockets 139 to release the finished workpiece 137.

The workpiece 137 is pressed downwardly on the polishing table 45 by springs 147 (FIG. 10) one of which is positioned around each of a pair of pins 148 (see also FIGS. 8 and 11) that are threaded into the top surface of the pressure plate 134 near its ends, and that extend upwardly through clearance openings 149 in bridge p ates 150. As can also be seen in FIGS. 8 and 11, each of the bridge plates 150 is positioned across one end of its respective pressure plate 134 by a pair of threaded posts 151, the posts 151 being threaded into the retainer plate 116. The vertical position of the bridge plates 150 relative to the retainer plate 116 and thus the force exerted by the springs 147 on the pressure plate 134, is adjustable by varying the position of upper and lower sets of lock nuts 152 threaded on the post 151 above and below the bridge plates 150.

During a polishing cycle, as will be more fully described below, and after the workpiece 137 has been polished, compressed air is supplied to the air conduit 104 in the spindle 101 and thus to the cylinder 124 beneath its piston 128 to pull its piston rod 125 upwardly, lifting the pressure plate 134 and the workpiece 137 which is retained thereon above the level of the table 45 and against the pressure of the springs 147. After the polished workpiece 137 is removed by releasing the vacuum in the vacuum pockets 139 and a rough or unpolished workpiece 137 is placed on the pressure plate 134, air pressure in the line 127 and beneath the piston 128 is relieved allowing the springs 147 to expand and to urge the pressure plate 134 downwardly with predetermined pressure. Freedom of movement of the piston 128 is assured by reason of an exhaust vent 153 in the cylinder 124 at a level above the piston 128.

The cylinder 124 is rigidly connected to the body of the valve 142 and the support bracket 121 by machine screws 154, and the body of the valve 142 is also supported on the loading guide 116 by an outboard bracket 155 that is fixed on the loading guide 116 by a machine screw 156.

A spindle drive motor 157 (see FIGS. 1 and 2) is mounted on top of the top plate 49 by a motor base plate 158 which is carried on a motor and transmission support plate 159. The motor base plate 158 is connected to the support plate 159 by machine screws 160 which extend through elongated slots 161 in the base plate 158. An adjustment screw 162 is engaged with an ear 163 on the motor base plate 158 and with a flange 164 on the support plate 159. The support plate 159 is, in turn, adjustably mounted on the main top plate 49 by machine screws 165 which extend through elongated slots 166 in the support plate 159 and its position may be adjusted by means of an adjusting screw 167 extending through an ear 168 on the top plate 49 and threadably engaged with the flange 164 on the support plate 159.

A drive belt 169 is engaged with a motor pulley 170 and with an input pulley 171 of a reduction gear box 172 which is also mounted on the support plate 159. Adjustment of the position of the motor base plate 158 on the support plate 159 provides for tensioning the belt 169. A gear box output pulley 173 drives a transmission belt 174 which is also engaged with a pulley 175 keyed to the upper end of a jack shaft 176. The jack shaft 176 is rotatably journaled in bearings 177 that are mounted on the forward vertical face of a heavy jack shaft bracket 178 erected on the front side of the top plate 49 so that the jack shaft 176 extends downward parallel to the tubular drive shaft 74 and the spindles 101 (see also FIG. 4).

A spindle drive belt 179 (see also FIG. 3) is engaged with a pulley 180 pinned to the lower end of the jack shaft 176 and is also engaged at all times with a least two of the three spindle pulleys 106. Referring particularly to FIG. 3, it will be seen that as the head 93 rotates, the several spindles 101 are revolved around the center defined by the drive shaft 74 while remaining in driving contact with the spindle drive belt 179 except during the approximately 30 of circumferential movement at the front of the machine. The drive belt 179 is shown in FIG. 3 in solid lines while it is in engagement with two of the spindle drive pulleys 106a and 106b at the rear of the machine, and out of engagement with the spindle drive pulley 1060 of the spindle 101 located at the front center of the machine. The spindle drive belt 179 is shown in dotted lines, indicated by the reference number 179a in FIG. 3, when it is engaged with all three of the spindle drive pulleys 106a, 1061) and 1060 indicated by the dotted lines. During the rotary movement of the head 93 (clockwise in FIG. 3), while one of the spindle drive pulleys 1060 is disengaged from the spindle drive belt 179, valving means to be later described, is automatically actuated to feed air through the air line 109 to the bottom of the spindle cylinder 107 to pull its rod 110 upwardly lifting the particular spindle 101 and its fixture 115 to the upper position, as shown at the left in FIG. 4. The particular spindle 101 coasts to a stop during the disengagement of its pully 106 from the spindle drive belt 179, enabling the operator to remove a polished workpiece 137 and to replace it with a rough workpiece 137.

A belt tensioning device 181 (FIGS. 1 and 3) is engaged with the belt 179 at all times, being mounted on the end of a spring urged rocker 182 that is pivotally mounted on a finger 183 mounted on the jack shaft bracket 178.

A rotating slurry trough 184 is carried by three trough brackets 185 (FIG. 4), each of which is mounted on and extends outwardly from one of the vertical end plates 99 of the spindle brackets 96. The slurry trough 184 rotates with the head 93 and the spindles 101 and delivers slurry to the surface of the grinding table 45 through a depending pipe 186 with the rate of flow therethrough being controlled by a valve 187. Grinding slurry is supplied to the trough 184 from a supply tank 188 (FIG. 1) through a pipe 189, the rate of flow being controlled by a cock 190 connecting the pipe 189 to a nozzle 191 which overlies the slurry trough 184.

OPERATION Referring now particularly to FIGS. 5 and 6, compressed air is fed through the air source conduit 76 and the air passageway 80 to the air nipple 87 and thence downwardly through the air supply line 88 interiorly of the tubular drive shaft 74. The line 88 is connected to an air manifold 192 and, through air lines 193 to air valves 194 for the spindle lowering cylinders 107. Each of the air valves 194 is mounted on the side of the associated one of the spindle brackets 96 and is connected by the air lines 108 and 109 to the top and bottom, respectively, of one of the spindle air cylinders 107. Each of the air valves 194 is controlled by a pair of pilot valves 195 and 196 (see also FIGS. 4-7) which are positioned in a vertical plate 197 carried on and extending upwardly from its respective spindle bracket 96. Each valve 194 is connected by pilot valve lines 198 to its pilot valves 195 and 196. The pilot valves 195 and 196 have small inwardly directed plungers which are successively engaged by projections 199 and 200 protruding from the outer wall of the main drive shaft housing 70. The compressed air manifold 192 is also connected by air lines 201 to three valves 202. Each of the valves 202 is mounted by a small bracket 203 on the inner rim of the coolant trough 184 and is connected by an air line 204 to the respective one of the rotary couplings 105 on one of the spindles 101. As has earlier been explained, this connects the compressed air manifold 192 to the annular air conduit 104 in the spindle 101 and thence to the air lines 127 and to the three cylinders 124 of the fixtures 115. Each of the air valves 202 is controlled by a pair of pilot valves 205 and 206 that are mounted on the plate 197 (see FIGS. 7) in line to be engaged by the projections 199 and 200. The pilot valves 205 and 206 are connected to the respective valve 202 by a pair of pilot valve lines 207. Each of the valves 202 also has an exhaust vent 208.

As can best be seen by reference to FIGS. 6 and 8, the air supply through the manifold 192 to the respective valves 194 and 202 and thus to the fixture lifting cylinders 107 and the air cylinders 124 is controlled by the pilot valves 195, 196, 205 and 206. The two projections 199 and 200 are spaced circumferentially around the housing 70 a distance indicated in FIG. 7 by the letter y. This distance, when added to the horizontal distance between the pilot valve 206 and the pilot valve 196, indicated by the letter x in FIG. 7, comprises 35 of angular rotation of the head 93 and thus of the fixtures 115. This is the area at the front of the machine wherein the spindle drive pulleys 106 are out of engagement with the spindle drive belt 179 as has been discussed above with reference to FIG. 3.

As the head 93 rotates in the direction of movement indicated by the arrow on the plate 197 in FIG. 7 (clockwise in FIG. 5), the pilot valve 206 is first engaged by the projection 199. This actuates the respective valve 202 to supply air under pressure to the air cylinder 124, thus to lift its particular pressure plate 134 and raise a workpiece 137 off of the table 45. Immediately thereafter, the pilot valve 195 engages the projection 199 to actuate the valve 194 and deliver air under pressure through the air line 109 to the bottom of the spindle air cylinder 107. This raises the entire fixture 115 to its upper position (FIGS. 4 and 6) and, because the spindle drive pulley 106 of that fixture is no longer engaged with the spindle drive belt 179 (FIG. 3), this fixture 115 comes to a stop to allow the operator to remove the polished workpieces 137 from that fixture 115 and replace them with fresh workpieces 137. As the head 93 continues to rotate and approaches the limit of the 35 loading area, the operator has removed the polished workpieces from the three pressure plates 134 of the particular fixture 115 and has reactivated the vacuum to hold the workpieces 137 in place.

At this point, the pilot valve 196 engages the projection 200 and actuates the respective valve 194 to apply air through the line 108 to the cylinder 107. This extends the piston rod 110 and lowers the respective fixture 115 back downwardly to its lower or operating position. Immediately thereafter, the pilot valve 205 engages the projection 200 and actuates the respective valve 202 opening the valve 202 to exhaust through its vent 208 and relieving the lifting pressure in the particular air cylinder 124 from beneath the piston 128. This allows the pressure springs 147 to thrust the pressure plates 134 of that fixture 115 downwardly, bringing the workpieces 137 into engagement with the table 4.5.

As each successive one of the fixtures 115 completes its single revolution around the machine, it reaches the front loading area and the respective ones of the pilot valves 195, 196, 205 and 206 are actuated in the sequence:

' 8 (1) pilot valve 206 to lift the workpiece 137 off of the table 45; (2) pilot valve 195 to raise the fixture 115; (3) pilot valve 196 to lower the fixture 115; (4) pilot valve 205 to relieve the lifting pressure in the respective cylinder 124.

The main vacuum line 89 extending downwardly through the head drive shaft 74 is connected to a vacuum manifold 209 that is secured to the air manifold 192' (FIG. 5) and carried around with the head 93. The vacuum manifold 209 is connected by vacuum lines 210 to the rotary couplings on the spindles 101 and then through the vacuum conduits 103 (FIG. 9) and the lines 143 to the manually operable valves 142. Because the valves 142 are manually controlled by an operator, as described above, no additional valving is provided in the vacuum system.

In order to facilitate the insertion of rough workpieces 137 into their respective cut outs 117, the operator may employ a device such as the hand fixture 211 shown in FIG. 4 by which he can lift a rough workpiece 137 upwardly to insert it through a cut out 117 in the loading guide 116 and up against the undersurface of the pressure plate 134, holding the workpiece 137 in place while he actuates the valve 142 to reapply vacuum into the pockets 139. Because each of the individual pressure plates 134 has its own vacuum line 143 (FIGS. 8 and 9) which is controlled by its respective Valve 142, actuation of one of the individual valves 142 has no effect, of course, upon the vacuum present in the pockets 139 of the other two pressure plates 134 of that particular fixture 115.

Having described our invention, we claim:

1. A machine for polishing the flat front surfaces of a plurality of identical, plate-like workpieces, said machine comprising, in combination, a rotatable flat polishing table and means for rotating the table at a constant speed, a spider-like head mounted for rotation on an axis concentric with the axis of rotation of said table, a plurality of fixtures carried by said head and individually rotatable therein on axes parallel to the axis of rotation of said head for revolution around said axis in planetary relationship thereto, means for rotating each of said fixtures, each of said fixtures having a shaft and a disc-like loading guide at the lower end of said shaft, said guide lying generally parallel to the surface of said polishing table, means for moving each of said guides between a working position adjacent said polishing table and a loading position remote therefrom, a plurality of platen-like'workpiece holders carried by each of said fixtures, said holders having surfaces complementary to the back surfaces of the workpieces for holding the front faces thereof parallel to the surface of said table, individually releasable means for retaining each workpiece against the respective one of said workpiece holders, and means mounted on said fixtures for resiliently urging each of said workpiece holders toward and the respective workpieces against the surface of said table.

2. A machine according to claim 1 in which the means for rotating said fixtures comprises, in combination, a fixture drive pulley mounted on the upper end of each of said fixture shafts, a belt extending generally circumjacently of the axis of rotation of said head, and engageable with said fixture pulleys when said fixtures are in Working position, a belt drive shaft mounted on said machine for rotation on an axis parallel to and spaced from the axis of rotation of said head, a belt drive pulley mounted on said belt drive shaft and continuously engaged with said belt, the axis of rotation of said belt drive shaft lying outside of the path of revolution of the axes of said fixture drive shafts a distance such that, and the diameter of said belt drive pulley being such that, each of said fixture drive pulleys disengages from said belt as the respective one of said fixtures reaches a predetermined position near said belt drive shaft and passes between said belt drive shaft and the axis of rotation of said head and re-engages with said belt after said fixture reaches a second predetermined position beyond said belt drive shaft.

3. A machine according to claim 2 and control means actuated after disengagement of each of said fixture drive pulleys from said belt for actuating the respective one of said means for moving said fixture guides from working position to loading position and for returning said fixture guides to working position before said fixture reaches the position of re-engagement of said fixture drive pulley with said belt.

4. A machine according to claim 2 in which each of said means for moving each of said fixture guides between working and loading positions is a vertical double acting fixture air cylinder and each of said means for resiliently urging each of said workpiece holders toward said table is a vertical double-acting holder air cylinder and in which said control means comprises a pair of valves for each fixture air cylinder and a pair of valves for all of said holder air cylinders on the respective fixture, each group of four of said valves for a fixture being mounted on said head and rotatable therewith, and a pair of valve actuators positioned for engagement by said valves during the period when the respective one of said fixture drive pulleys is disengaged from said belt in the sequence: workpiece holder raised, fixture raised, fixture lowered and workpiece holder lowered.

5. A machine according to claim 1 in which said polishing table is horizontal and is mounted on the upper end of a vertical shaft, said spider-like head is mounted on the lower end of an overhead shaft coaxial with said table shaft and the means for moving the loading guides are air cylinders carried by said head and yoked to said fixture shafts for vertically moving each of said fixtures.

6. A machine according to claim 1 in which each of the loading guides is a horizontal disc having a plurality of cutouts therethrough that are equidistantly spaced around the fixture shaft, each cutout being of substantially the same shape as and slightly larger than an individual workpiece and in which each of said workpiece holders is positioned above a respective one of said cutouts for holding a workpiece in the respective cutout with its front surface protruding beyond the surface of said disc.

7. A machine according to claim 6 in which each of said workpiece holders comprises an air cylinder and piston rod carried on said disc that is centered above the respective one of said cutouts and the means for retain ing a workpiece on said holder comprises a hollow platen mounted on the end of said piston rod and engaging the back surface of the workpiece, a vacuum line connected through said fixture shaft to said platen and a manual valve in said vacuum lines for each of said platens.

8. A machine according to claim 1 and an annular polishing slurry trough supported in position underlying said polishing table and extending upwardly and around the edge of said table for collecting slurry thrown off of said table by rotation and revolution of said fixtures.

References Cited UNITED STATES PATENTS 626,895 6/1899 Fondu S1133 X 266,840 10/1882 Kelly 51-133 971,861 10/1910 Nickerson 51-133 2,963,830 12/1960 Hook 51131 HAROLD D. WHITEHEAD, Primary Examiner @3 3 UNITED STATES PATENT OFFICE CERTIFICATE OF 'CQRRECTION PacentNo. 15%.158 Dated v m r 17, 1970 Inventor(s) w. E. Reaser, et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 60, after "of a" insert portion Column 6, line 15, after "with" delete "a" and inse:

$|GND PM $ERLED F E B 12 3 \971 U Aueot:

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' commissioner of Patent: 

